Track shunting apparatus



Aug. 10, 1937. c BUTLER ET AL 2,089,825

TRACK SHUNTING APPARATUS Original Filed Jan. 5, 1953 IN VENTORS Charles W li'arzler area B y Benz 20rd 0 Flagarz ki l L THEIR A TTORNEY Patented Aug. 10, 1937 UNITED STATES PATENT OFFIQE TRACK SHUNTING APPARATUS Application January 5,

1933, Serial No. 650,300

Renewed June 18, 1936 10 Claims.

Our invention relates to track shunting apparatus, and more specifically to apparatus for shunting track circuits by light weight rail vehicles having steel wheels or pneumatic tired 5 wheels.

We will describe one form of track shunting apparatus embodying our invention, and will then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing one form of apparatus embodying our invention.

For effective shunting, it is necessary to penetrate the resistance film which is usually found on the rail surface. In the case of heavy rolling equipment, the weight of the equipment itself is generally suflicient to accomplish this result, but with rail vehicles of light weight, such as the gas-electric car for example, it has been found expedient to use auxiliary apparatus for breaking down the rail film by means of voltage applied to the rail surface. To break down the rail film initially, an appreciable voltage is required, but once breakdown has occurred, a low resistance path can be maintained at a relatively low voltage value, provided a relatively large current is maintained in the breakdown path. To meet both requirements of relatively high voltage and high current, a source of considerable power output would be required aboard the car.

In order to avoid the necessity for excessive power, we have provided two separate sources, one of high voltage and low current capacity for initial breakdown of the rail film, and the other of low voltage and high current capacity for maintaining a low resistance path through the rail film.

Referring to the drawing, the apparatus illus trated is intended to be carried on a rail car,

arranged to travel on rails I and 2 of the track.

The reference character G designates a low frequency, low voltage, and high current generator, which is driven by a motor M energized from the car battery CB. Generator G similarly driven, is a high frequency, high voltage, and low current generator. Since the shunting apparatus at the forward end of the car is similar to that at the rear end, it will be sufficient for our purpose to describe but one group of this apparatus.

Considering the left-hand group of shunting apparatus, the voltage of the high frequency gen erator G is stepped up through transformer T and is applied across rails I and 2 by means of rail shoes 3 and 4, through the series condenser 55 C Condenser C offers a relatively low impedance to currents of high frequency, but acts as a blocking condenser and prevents appreciable quantities of low frequency current, supplied by step-down transformer T from flowing in the secondary winding l5 of transformer T Filter condenser C therefore prevents the short-circuiting through winding [5, of the low frequency voltage of secondary winding 12 of transformer T which is energized from the low frequency, high current generator G Another function of condenser C is to limit the maximum amount of high frequency currency supplied from generator G when the rail film is completely broken down. To prevent short-circuiting of the high frequency voltage by winding l2, a suitable condenser C is connected across this winding, tuning the winding so that it will offer a high impedance to the high frequency current. If the two frequencies are chosen so as to have a substantial separation, currents of the undesired frequency can be effectively blocked so that neither of the two current sources G or G will take an appreciable amount of power from the other. If the frequency separation is large and the impedances of the circuits of transformers T and 'I are suitably chosen, condensers C and C may be dispensed with, dependence being placed on the impedance of the above circuits to the undesired frequency to prevent an appreciable interchange of current between the two sources. The use of condensers C and C will, however, increase the power economy of the system.

Condenser C is used to tune winding I5 to the high frequency current in order that the magnetizing current of transformer T will be as low as possible, to conserve the output of generator G Rail shoes 5 and 6, joined by the cable [1, provide a return path for the currents from transformers T and T and serve also to shunt the track, since the impedance of cable I! will usually be lower than the impedance of the windings and connections which join rail shoes 3 and 4. The purpose of reactor X in series with transformer T is to limit the maximum value of the rail film current so as to avoid unnecessary drain on generator G and the car battery. This reactor also serves to increase the impedance of the circuit of transformer T to the flow of the high frequency current from generator G In series with winding l2 of transformer T is connected the primary winding I3 of a current transformer T which energizes the indication relay K through a rectifier R When the rail film resistance has been decreased sufficiently, as determined by the magnitude of the rail film ourrent, to enable satisfactory shunting of the track to be obtained, relay K will pick up, closing the energizing circuit for indicator L over front contact 25 to provide a visual indication of the safe shunting condition.

Instead of using generator G the high frequency voltage can be obtained from a vacuum tube oscillator, although, in such case, it may be necessary to provide a separate oscillator for the shunting apparatus at each end of the car because of the inherently poor voltage regulation of this type of oscillator. That is, if an oscillator is used, the breakdown of the film at one end of the car may reduce the voltage at the other end of the car sufiiciently to prevent satisfactory operation. The filament current for the oscillator can be supplied from the car battery CB and the plate voltage from a step-up transformer and rectifier combination energized from the generator G or this voltage and current can be supplied in any other suitable manner.

It will be apparent that by using the apparatus disclosed, it is possible to break down the rail film and to maintain a low resistance'track shunting path with a lower expenditure of energy than 'would be required were both the high voltage and high current supplied from the same source.

The invention claimed in the present applica tion is an improvement on the apparatus disclosed and claimed in an application for Letters Patent of the United States filed by Howard A. Thompson on August 16,1932, Serial No. 629,030, for Apparatus for decreasing rail contact resistance.

, Although we have herein shown and described only one form of apparatus embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is; V

1. In combination with a rail vehicle and a section of railway track, a source of relatively high frequency and low current on said vehicle, another source of relatively low frequency and high current on the vehicle, a pair of rail shoes one for each rail of said track, a circuit for applying a high voltage from said high frequency s'ourceand a low voltage from said low frequencysource across said rail shoes for decreasingthe rail film resistance to improve shunting of said track, and an electric filter for each source for decreasing the interchange of current between said two sources. 7 a l 2. In combination with a rail vehicle anda section of railway track, a pair of rail shoes one for each rail of said track and joined together electrically, means including a first source of high Voltage on said vehicle for applying a potential across said rail shoes for breaking down the rail film between said rail shoes and the rail surface, and means including a second source of high current also on said vehicle for maintaining. .the' fiowof a substantial current, between said rail shoes and the rails after breakdown of the film for maintaining a. low resistance shunting path to aid shunting of said track by said rail shoes.

3. Apparatus for shunting a track including a pedanceto form'a shunt path from one to the other rail, means for applying .a relativelyhigh potentiallfrom a high frequency low. current source across said railshoes for breaking down the resistance film between said rail shoes and the rail surface, means for supplying a relatively low potential from a low frequency high current source across said rail shoes for maintaining the fiow of a relatively'large current through the rail film to maintain a low resistance contact between said shoes and the rail surface to aid shunting of said track, and an electric filter for each source connected in such manner as to decrease the interchange of current between said two sources and so to economize the power output of each of said sources.

4. In combination with a rail vehicle and a section of railway track, a pair of rail shoes one for each'rail of the track, two transformers on the vehicle, each having a primary winding and each having a secondary winding connected across said rail shoes, a high frequency low current source on the vehicle for energizing the primary winding of one of said two transformers to induce a relatively high voltage'in the secrail surface to aid shunting of said track by said 7 rail shoes, and two condensers, one connected inseries with the secondary winding of saidone transformer for preventing the flow of current from said low frequency source in said one transformer and the other connected in parallel with the secondary winding of said other transformerfor preventing the fiow of current from said high frequency source in said other transformer, thereby economizing the power output of said two sources.

5. In combination with a rail vehicle and a section of railway track, a first pair of rail shoes one for each rail of the track, a second pair of rail shoes one for each rail of the track and connected together by a low impedance conducrent source on the vehicle connected across said first pair of rail shoes for breaking down the rail film between said first and second rail shoe pairs and the rail surface, a low frequency low voltage and high current source on the vehicle connected 1 across said first pair of rail shoes for maintaining the fiow of a substantial current through the rail film between said first and second rail shoe pairs and the rail surface to maintain a low resistance shunting path for shunting said track by said second rail shoe pair, an electric filter connected in such manner as to decrease the flow of current from one to the other source, and a reactor between said first rail shoe pair and said low frequency source for limiting the magnitudeof the current supplied from said low frequency source.

6. Means for providing a low resistance path between two conducting members making-imperfect electrical contact with each other without an excessive expenditure ofpower, consisting of two sources, one of high frequency and low current for supplying a relatively high potential across I said members for breaking down the resistance pair of rail shoes omed together through an imfilm therebetween, and the other of low frequency and high current for maintaining the flow of a relatively large current between said members once the film has been broken down, an electric filter connected between said two sources in such manner as to decrease the fiow of current from tor, a high frequency high voltage and low cur-.5145

one to the other source, and means governed in accordance with the magnitude of the current flowing between said two conducting members for indicating that said resistance film has been broken down.

'7. Means for providing a low resistance path between two conducting members making imperfect electrical contact with each other without an excessive expenditure of power, consisting of two sources, one of low current for supplying a relatively high potential across said members for breaking down the resistance film therebetween, and the other of high current for maintaining the flow of a relatively large current between said members once the film has been broken down, means for decreasing the interchange of current between said two sources, and means governed in accordance with the magnitude of the current flowing between said two conducting members for indicating that said resistance film has been broken down.

8. Apparatus for aiding the shunting of a track by a rail vehicle comprising, in combination, means for applying a relatively high potential to the rails of said track from a low current source carried on said vehicle for breaking down the resistance film on the rail surface, and means for supplying a relatively high current to said rails from a low potential source also carried on said vehicle for maintaining the flow of a relatively large current from said low potential source once said rail film has been broken down.

9. Apparatus for aiding the shunting of a track by a rail vehicle comprising, in combination, a train-carried track shunt, train-carried means for starting the flow of an initial current through the rail contacting portions of said shunt to break down the resistance film on the rail surface, and other train-carried means for maintaining the flow of current through said track shunt once said rail film has been broken down.

10. Apparatus for aiding the shunting of a track by a rail vehicle comprising, in combination, a low impedance train-carried conductor for bridging the track, train-carried high voltage means for starting the flow of an initial current through said conductor to break down the rail resistance film between said bridging conductor and the track, and low voltage train-carried means for maintaining the flow of current through said conductor once said film has been broken down.

CHARLES W. BUTLER. BERNARD E. OHAGAN. 

